How Do Scientists Study Ancient Climates?

Scientists use tools, such as the increment borer featured here, to obtain tree-ring samples. These samples can then be studied to determine the climate conditions during the life of the tree. Photo Credits: Edward Cook Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York

Scientists study Earth’s climate and the ways that it changes in a variety of different ways, using satellite, instrumental, historical, and environmental records. One challenge of using satellite and instrumental data is that their lifespans have been rather short when compared to Earth’s life. The satellite record is only a little over 20 years old and the instrumental record only extends back into the 19th century. Both of these records can be too short to study certain climate processes that occur over hundreds to thousands of years.

To extend those records, paleoclimatologists look for clues in Earth’s natural environmental records. Clues about the past climate are buried in sediments at the bottom of the oceans, locked away in coral reefs, frozen in glaciers and ice caps, and preserved in the rings of trees. Each of these natural recorders provides scientists with information about temperature, precipitation, and more. Many of these have some type of layers, bands, or rings that represent a fixed amount of time, often a year or growing season. The layers vary in thickness, color, chemical composition, and more, which allows scientists to extrapolate information about the climate at the time each layer formed.

Scientists can then take the records left by many different types of natural records and combine them to get an overall picture of the global climate. Typically, records that have large timespans have less detail about short-term climate changes, while shorter records are often more detailed. To combine them, scientists must use records with similar levels of temporal detail or account for these disparities to accurately paint a picture of ancient climates.